关于android:handler实现精确计时

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首先说下对于 handler 本身的误差:

如果应用 handler.postDealyed(……, 1000) 形式来进行每秒的计时,是不精确的,是的,有很大误差,误差的起因在于在你收到音讯,到你从新收回 handler.postDealyed 的工夫,并不是霎时实现的,这外面有很多逻辑解决的工夫,即便没有逻辑解决的工夫,handler 自身也是耗损性能的,所以音讯并不可能依照现实的 1000 提早来进行发送,这就导致了误差的累积。

代码:

时钟接口:

public interface IDigitalClock {
/**
* 开始计时
*/
void start();
/**
* 进行
*/
void stop();
/**
* 时钟复位
*/
void reset();
/**
* 重启
*/
void restart();}

正计时时钟:

import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.os.SystemClock;
import android.util.Log;
import java.text.DecimalFormat;
public class DefaultDigitalClock implements IDigitalClock {
private final static String TAG = "DefaultDigitalClock";
private final static int TICK_EVENT = 0x1001;
private Ticker mTicker;
private Handler handler = new Handler(new Handler.Callback() {
@Override
public boolean handleMessage(Message msg) {if (msg.what == TICK_EVENT) {long seconds = (long) msg.obj;
String HHMMss = formatElapsedTime(seconds);
clock.tick(seconds, HHMMss);
}
return false;
}
});
private long startTime;
private long elapsedSeconds;
private long maxSeconds;
private ClockOnMainThread clock;
public DefaultDigitalClock(ClockOnMainThread clock) {this(-1, clock);
}
public DefaultDigitalClock(long maxSeconds, ClockOnMainThread clock) {
this.maxSeconds = maxSeconds;
this.clock = clock;
this.elapsedSeconds = -1;
this.startTime = -1;
}
@Override
public void start() {startTime = System.currentTimeMillis();
mTicker = new Ticker();
long now = SystemClock.uptimeMillis();
long next = now + (1000 - now % 1000);
handler.postAtTime(mTicker, next);
}
@Override
public void stop() {handler.removeMessages(TICK_EVENT);
if (mTicker != null) {handler.removeCallbacks(mTicker);
}
}
@Override
public void reset() {
elapsedSeconds = -1;
startTime = -1;
handler.sendMessage(newTick(0));
}
@Override
public void restart() {stop();
reset();
start();}
/**
* 在每秒的整点执行
* {@link "https://blog.csdn.net/cpcpcp123/article/details/88542113"}
*/
private final class Ticker implements Runnable {public void run() {onTimeChanged();
// 在设定秒数后完结
if (maxSeconds > 0 && elapsedSeconds == maxSeconds) {stop();
return;
}
long now = SystemClock.uptimeMillis();
long next = now + (1000 - now % 1000);
handler.postAtTime(this, next);
}
};
/**
* 计算工夫变动
*/
private void onTimeChanged() {if (Thread.currentThread() != Looper.getMainLooper().getThread()) {Log.e(TAG, "onTimeChanged() must work on main thread!");
return;
}
elapsedSeconds = (System.currentTimeMillis() - startTime) / 1000;
Log.d(TAG, String.valueOf(elapsedSeconds));
String HHMMss = formatElapsedTime(elapsedSeconds);
clock.tick(elapsedSeconds, HHMMss);
}
private Message newTick(long seconds) {Message msg = new Message();
msg.what = TICK_EVENT;
msg.obj = seconds;
return msg;
}
/**
* @see android.text.format.DateUtils#formatElapsedTime(long)
* @param elapsedSeconds 通过的秒数
*/
private String formatElapsedTime(long elapsedSeconds) {
// Break the elapsed seconds into hours, minutes, and seconds.
long hours = 0;
long minutes = 0;
long seconds = 0;
if (elapsedSeconds >= 3600) {
hours = elapsedSeconds / 3600;
elapsedSeconds -= hours * 3600;
}
if (elapsedSeconds >= 60) {
minutes = elapsedSeconds / 60;
elapsedSeconds -= minutes * 60;
}
seconds = elapsedSeconds;
String hh = new DecimalFormat("00").format(hours);
String mm = new DecimalFormat("00").format(minutes);
String ss = new DecimalFormat("00").format(seconds);
return String.format("%s:%s:%s", hh, mm, ss);
}
public interface ClockOnMainThread {void tick(long seconds, String time);
}
}

参考博客

  • handler 实现准确计时的两种形式
  • Android 计时罕用的 7 种形式

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